1. Field of the Invention
The present invention relates to a technical field of a surface-mounting type semiconductor device, and particularly to a technical field of a surface-mounting type semiconductor device having a leadless structure.
2. Background Art
Generally, a semiconductor device includes a metallic lead frame as one component thereof, and micromachining for the pitch of leads in the lead frame is required for forming a greater number of pins therein. However, if attempting to reduce the width of each lead itself, the strength of the lead is lowered, and a short circuit may tend to occur due to bending or similar deformation of the lead. Accordingly, it is unavoidable to upsize the package in order to ensure the pitch of each lead. Thus, a semiconductor device including a lead frame tends to have a package of a greater size and thickness. Therefore, a surface-mounting type semiconductor device having a leadless structure has been proposed.    Patent Document 1: TOKUKAIHEI No. 9-252014, KOHO    Patent Document 2: TOKUKAI No. 2001-210743, KOHO
A semiconductor device described in the Patent Document 1 is shown in FIGS. 9(a) and 9(b). The method of producing the semiconductor device comprises attaching a metal foil onto a base material 101 and etching it such that the metal foil remains at predetermined portions, fixing a semiconductor element 102 onto a metal foil 103a (die pad) having substantially the same size as that of the semiconductor element 102 by using an adhesive 104, electrically connecting the semiconductor element 102 and metal foils 103b via wires 105, and transfer molding the connected structure with a sealing resin 106 using a mold (FIG. 9(a)). Finally, the molded sealing resin 106 is removed from the base material 101 to form a package of the semiconductor element (FIG. 9(b)). However, in the semiconductor device formed by this production method, the adhesive 104 and the metal foil 103a (die pad) are associated with the semiconductor element 102. Therefore, there still is a need for a semiconductor device which has a smaller size and a thinner shape.
FIGS. 10(a) and 10(b) illustrate a semiconductor device described in the Patent Document 2. Generally, the semiconductor device is produced by the following method. First, a metal plate 201 is obtained by forming square-shaped concave grooves 201a in a metal plate 201 used as a base material. Next, a semiconductor element 202 is fixed onto the metal plate 201 using an adhesive 203, wires 204 are then provided by wire bonding at positions required for a design, thereafter the so formed structure is transfer molded with a sealing resin 205 (FIG. 10(a)). Subsequently, the metal plate 201 and adhesive 203 are grinded together, and the metal plate 201 is cut with the sealing resin 205 in accordance with dimensions conforming to the design so as to obtain a semiconductor device (FIG. 12(b)). However, also in this method, the semiconductor device obtained is associated with the adhesive layer 203 and the metal plate 201 under the semiconductor element 202. Therefore, it is difficult to obtain a thinner-type semiconductor device as desired in the art.
Thus, in the conventional methods, it is difficult to obtain a thinner type semiconductor device. Accordingly, in order to obtain a thinner type semiconductor device, the semiconductor element (chip) itself must be grinded into a thinner one, thus increasing occurrence of breakage or cracks in the semiconductor element during such a production step and hence leading to increase of the cost.
In such a one-side-sealed type semiconductor device, ground bonding is sometimes provided on a die pad after a semiconductor element is loaded onto the die pad. In this case, a bonding portion is formed in the same plane as the bottom face of the semiconductor element. Thus, due to the difference in thermal expansion between the semiconductor element, substrate and sealing resin, if peeling occurs along the boundary between the sealing resin and the substrate from an outer periphery of the bottom face of the semiconductor element, such peeling eventually causes the wires in the ground bonding portion provided in the same plane to be peeled off at the same time, as such leading to an electrically opened state.